Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.93	3.278%	$106.304	$106.30	$106.30	$106.30
Purchase #2	$69.46	4.124%	$72.3245	$72.32	$72.30	$72.30
Purchase #3	$40.25	13.302%	$45.6041	$45.60	$45.60	$45.60
Purchase #4	$156.78	10.708%	$173.568	$173.57	$173.55	$173.60
Purchase #5	$146.50	12.648%	$165.0293	$165.03	$165.05	$165.00
Purchase #6	$5.86	12.734%	$6.6062	$6.61	$6.60	$6.60
Purchase #7	$125.85	5.412%	$132.661	$132.66	$132.65	$132.70
7 purchase totals =	$647.63		$702.0971	$702.09	$702.05	$702.10